The invention relates generally to semiconductor manufacturing and integrated circuits and, more particularly, to device structures for an anti-fuse and methods for manufacturing these device structures.
Anti-fuses are nonvolatile, once-programmable devices widely used, among other device applications, in programmable integrated circuits. A common use of anti-fuses is in redundancy circuits of dynamic random access memories and static random access memories. Another common use of anti-fuses is in programmable read-only memories and programmable logic devices (PLDs) to program logic circuits to create a customized design. Yet another common use of anti-fuses is to program the input/output (I/O) configuration of a memory device.
An anti-fuse is initially non-conductive at the time of its fabrication, but may be irreversibly programmed to create a permanent conductive link. In a common construction, an anti-fuse includes a pair of conductive terminals separated by a dielectric layer. To program an anti-fuse, a predetermined voltage is applied as a bias potential across the terminals so that an electrical current breaks down the dielectric layer and thereby significantly reduces the electrical resistance of the anti-fuse. The reduced electrical resistance of the dielectric layer creates a closed conductive link or short between the conductive terminals. Once programmed, the anti-fuse cannot be programmed back to an open state with a high electrical resistance. Programming voltages for anti-fuse structures may be on the order of four volts, which may make existing constructions for anti-fuses incompatible with advanced integrated circuit designs.
Improved structures for an anti-fuse and methods of fabricating an anti-fuse are needed.